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restaurant-search/geocache.go

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/*
* Copyright (c) 2015 Alex Yatskov <alex@foosoft.net>
* Author: Alex Yatskov <alex@foosoft.net>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
package main
import (
"encoding/json"
"io/ioutil"
"os"
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"time"
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"github.com/kellydunn/golang-geo"
)
type geoCoord struct {
Latitude float64
Longitude float64
}
type geoCache struct {
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filename string
data map[string]geoCoord
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ticker *time.Ticker
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coder geo.GoogleGeocoder
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}
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func newGeoCache(filename string) (*geoCache, error) {
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cache := &geoCache{
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filename: filename,
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data: make(map[string]geoCoord),
ticker: time.NewTicker(time.Millisecond * 200),
}
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if err := cache.load(); err != nil {
return nil, err
}
return cache, nil
}
func (c *geoCache) load() error {
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file, err := os.Open(c.filename)
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if os.IsNotExist(err) {
return nil
}
if err != nil {
return err
}
defer file.Close()
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return json.NewDecoder(file).Decode(&c.data)
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}
func (c *geoCache) save() error {
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js, err := json.MarshalIndent(c.data, "", " ")
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if err != nil {
return err
}
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return ioutil.WriteFile(c.filename, js, 0644)
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}
func (c *geoCache) decode(address string) (geoCoord, error) {
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if coord, ok := c.data[address]; ok {
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return coord, nil
}
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<-c.ticker.C
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point, err := c.coder.Geocode(address)
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if err != nil {
return geoCoord{}, err
}
coord := geoCoord{point.Lat(), point.Lng()}
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c.data[address] = coord
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return coord, nil
}